1. Field of the Invention
The present invention relates to a bobbin winder tension application device for applying a tension to a bobbin thread drawn from a bobbin winder tube of a spool holder base when the bobbin thread is wound on a bobbin. A uniform and appropriate tension can be applied to the bobbin thread to be wound on the bobbin.
2. Description of Prior Art
A prior art bobbin winder tension application device of this type will be described with reference to FIGS. 1 and 6.
A spool holder base 2 attached to a table 3 of a sewing machine (hereinafter referred to as table) has a bobbin winder shaft 4 securely mounted thereon. A bobbin thread 8 wound on a bobbin winder tube 11 is inserted into and engaged with the bobbin winder shaft 4 and is guided via a thread hole 2b of the spool holder base 2. The bobbin thread 8 is unwound from the tube by bobbin winder tension application device 100 provided at a frame 1 of the sewing machine. This device then winds the thread on a bobbin 6 attached to the frame of the sewing machine. The bobbin thread 8 passes through the thread hole 2b of the spool holder base 2 then passes through a single thread hole 102 of a thread guide member 101 of the bobbin winder tension application device 100, then is elastically clamped between a pair of tension disks 103, 103, whereby a predetermined tension is applied to the bobbin thread 8, and finally is wound on the bobbin 6. A tension spring 105 is disposed between a tension shaft 104 and a tension adjusting nut 106 as illustrated in FIG. 6.
However, since the prior art bobbin winder tension application device 100 causes the bobbin thread 8 to pass through the single thread hole 102 of the thread guide member 101, then is clamped by the pair of tension disks 103, 103 whereby the predetermined tension is applied to the bobbin thread 8, the bobbin thread 8 is twisted in a spiral and when inserted into the pair of tension disks can slip off the tension disks 103, 103. This action occurs because the bobbin thread 8 as it is unwound from the thread bobbin winder tube 11 is drawn upwardly, namely, in the axial direction of the main shaft of the spool holder base.
Because of the twisting action the bobbin thread 8 is liable to slip off between the pair of tension disks 103, 103 which creates difficulties in winding the bobbin thread and lowers the working efficiency.